A global navigation satellite system (GNSS) is a system which can measure a position of a user using triangulation on the basis of signals received from an artificial satellite revolving around the earth. The GNSS may obtain various kinds of information about a position, a speed, a direction, a time, and the like of a user, a vehicle, or the like on the basis of the signals received from the artificial satellite. Among them, information about the position and the time may be calculated regardless of a change in the position of the user, while the speed and the direction are physical quantities calculated by movement of the user.
Vehicular navigation systems typically utilize the GNSS. Recently, as research into self-driving vehicles has increased, performance of a vehicle positioning system based on the GNSS has become important.
A method for estimating a direction on the basis of the GNSS, which uses a difference value of a movement amount generated by movement of the vehicle, suffers from a problem that the direction may not be recognized if the vehicle is stopped. In a system requiring a high level of positioning performance, such as those in self-driving vehicles, initial information about the position and direction of the vehicle is crucial in determining whether or not the vehicle departs. Therefore, in a self-driving vehicle, recognizing a direction of the vehicle even in a situation where the vehicle is stopped is necessary.